In the recovery of ore values, there are often process streams which may foam to an undesirable extent. For example, in recovering various metal values selectively from other values via froth flotation, a foam may occur which interferes with the ore value recovery. However, problems with foam may occur which impedes the mineral separation process. Additionally, problems with overfrothing may occur in many other kinds of streams. For example, industrial and municipal waste streams may also have foam control difficulties.
There are various ways for controlling foam, including altering or changing equipment to reduce turbulence which may be contributing to foaming. However, it will be appreciated that this method would likely be capital intensive and thus disfavored. If surfactants are used in a mineral processing stream, they could be removed or their proportion reduced since the surfactants may be stabilizing the foam bubbles. For example, hydrophobic solids can be used to lessen the effect of the foam stabilizing surfactants. The hydrophobic solids are attracted to the bubble interface where they absorb the surfactants and prevent them from stabilizing the bubbles.
Thirdly, a chemical that forms a monolayer film on the liquid, such as water, to increase its surface tension can effectively prevent a foam from forming. Lastly, a fourth technique is to increase the rate at which the bubbles coalesce to promote foam collapse. The goal is to dissipate the foam faster than it can form. Antifoaming compositions reduce surface and bulk viscosities, allowing bubble interface drainage to happen faster than the foam can be formed.
U.S. Pat. No. 3,837,489 describes an antifoam and process for the separation of molybdenum values associated with predominantly copper ores of the sulfide type. The antifoam, which is primarily directed to laundering or cleaning stages in the moly cycle, consists of a utilization of 1-60 ppm of a polyoxyethylene glycol ester in a hydrocarbon diluent per ton of ore. The oxyethylene fraction has a value of about 100-2,000 and an optimum value of about 400 and the fatty acid fraction is selected from C.sub.14 -C.sub.22 acids. A preferred antifoam of this patent is polyethylene glycol 400 dioleate (P. E. G. 400 dioleate) in kerosene or isoparaffin oil as the diluent. HLB values for the P. E. G. antifoam range from 5-12 with a preferred value of 5-10 for the dioleate.
However, it will be appreciated that while one composition may be suitable for controlling foam in some processes, that there are an appreciable number of variables which might make it unsuitable for a similar, but somewhat different process. It would thus be desirable if additional defoaming compositions could be developed which would have utility for one or more mineral processing streams.